When over 50 world leaders arrive in Sri Lanka mid-November for the Commonwealth summit, one prominent premier may be absent.

India’s Prime Minister Manmohan Singh is facing intense pressure from politicians representing his country’s Tamil community to boycott the meeting in protest at the Sri Lankan administration’s alleged failures to address human rights abuses committed against its own Tamil minority.

Much of the criticism relates to Sri Lanka’s long-running civil war that ended in 2009 with the defeat of the separatist Liberation Tigers of Tamil Eelam and was accompanied, particularly in its final months, by the deaths and displacement of thousands of Tamils.

A U.N. panel in 2011 said that over 40,000 people, mainly civilians from the island nation’s ethnic Tamils, died in the military’s final offensive which, according to the United Nations, included shelling in no-fire zones where Tamils had been encouraged to take refuge and the bombing of hospitals on the frontlines.

“What happened was nothing short of genocide of Sri Lankan Tamils,” said T.R. Baalu, a senior leader of the Dravida Munnetra Kazhagam party from Tamil Nadu state. “If the world can come together to take Syria to task, why is Sri Lanka being given special treatment?”

Critics of Sri Lanka’s human rights record also cite a growing list of continuing alleged atrocities, including accusations of the persecution of activists and journalists and the marginalization of Tamils. The U.N. Human Rights Commissioner Navi Pillay recently said Sri Lanka “is showing signs of heading in an increasingly authoritarian direction.”

Mr. Baalu said he had, during a meeting earlier this week, “strongly urged” Mr. Singh to boycott the summit. Mr. Singh said he would decide after “considering all relevant factors,” including the sentiments of the party and the Tamil people, an Indian news agency Press Trust of India reported.

On Thursday, Mr. Singh’s office and India’s Foreign Ministry said the prime minister had not yet decided whether he would attend the three-day summit that takes place once every two years and begins on Nov. 15 this year.

Tamil leaders are not alone in their protest. Last week, , Canadian Prime Minister Stephen Harper said he would not attend the meeting, although Canada would be represented. “The absence of accountability for the serious violations of human rights and international humanitarian standards during and after the civil war is unacceptable,” Mr. Harper said.

A U.K. parliamentary committee also criticized the country’s policy toward Sri Lanka, saying it should have taken a more “principled” stand in light of the “continuing serious human rights abuses.” The report said the UK should have made its participation in the summit conditional on improvements in human rights.

Meenakshi Ganguly, South Asia director of Human Rights Watch, said the decision to hold the meeting in Sri Lanka sent a signal to its leadership that the country’s “human rights record will be ignored.”

“Whether the prime minister goes or does not go, it is important for Sri Lanka to hear that there is continuing concern over its human rights violations,” Ms. Ganguly said.

India’s Tamil parties have long pressured the Indian government to take bolder steps to protect Sri Lanka’s Tamil population. The DMK has demanded an independent inquiry into alleged abuses in the final months of the war rather than relying on a government-sponsored commission “headed by the same people who want to protect the perpetrators of the crimes,” Mr. Baalu said. He blamed the Indian government for being weak in its response on behalf of the Tamil community.

India has voted in favor of two U.N. resolutions that criticized Sri Lanka’s inaction on bringing to justice those responsible for the human rights violations during the war. In doing do, New Delhi broke from its long-held position against interfering in another country’s domestic affairs. But the Tamil parties say the resolutions didn’t go far enough.

In March, the DMK, which was part of the Congress-led government, withdrew its support from the ruling coalition. It demanded that the government introduce stronger language in a U.N. resolution condemning Sri Lanka, specifically calling for the inclusion of the word “genocide.”

The summit will carry on whether or not Mr. Singh attends, but rights organizations have now turned their attention to the issue of the two-year chairmanship of the Commonwealth, which is set to go to Sri Lankan President Mahinda Rajapaksa after the meeting. Amnesty International’s India office has urged Mr. Singh to demand that Mr. Rajapaksa be denied the Commonwealth chair, usually granted to the country that hosts the meeting. Other organizations too are pushing leaders to reconsider.

“It’s bad enough that the Commonwealth has allowed a government accused of massive rights abuses and war crimes to host its summit,” said Brad Adams executive director of Human Rights Watch’s Asia division. “But to effectively put the Commonwealth in the hands of an unrepentant government that doesn’t meet the Commonwealth’s official values on democracy or human rights would be the height of hypocrisy.”